PIN FR solutions for polylactic acid biopolymers
Polylactic acid (PLA) is a biodegradable thermoplastic polymer produced from bio-resources such as corn starch, tapioca roots or sugarcane. However, the polymer is highly flammable and susceptible to dripping and brings the risk of spreading fire. Different PIN flame retardants have already been shown to be effective in polylactic acid polymers and blends (see pinfa Newsletter n°29). Bocz et al. tested ammonium polyphosphate and natural clay (montmorillonite) in all-PLA composites, produced by combining crystalline PLA fibres with amorphous PLA films. 16% PIN FR loading enabled a 40-50% reduction in peak heat release and total heat emission achieving UL94 V0 fire safety rating and enabling the polymer to be self-extinguishing.
With 33% FR dosing, dripping was fully suppressed. The PIN FR loading in the PLA did not significantly decrease the tensile and flexural strength of the polymer composite (probably because the PLA fibres were not modified), and increased stiffness, impact resistance and temperature dependent storage modulus. The PIN FRs tested were Clariant Exolit® AP 462, a micro-encapsulated ammonium polyphosphate (APP), and Rockwool Nanfil® 116, a non-treated montmorillonite (MMT). The authors note that this phosphorus PIN FRs is non-toxic and degrades to harmless plant nutrients.“Flame retarded self-reinforced poly(lactic acid) composites of outstanding impact resistance”, K. Bocz et al., Budapest University of Technology and Economics, Composites: Part A 70 (2015) 27–34 http://dx.doi.org/10.1016/j.compositesa.2014.12.005